N-aryl-n-alkyl-n{40 -arylthio ureas as herbicides

ABSTRACT

WHERE R is alkyl of one to about four carbon atoms, Y is halogen of atomic number 9 to 35, i.e., F, Cl and Br, alkyl of one to four carbon atoms, alkoxy of one to four carbon atoms or trifluoromethyl, with the proviso that when Y is alkyl or alkoxy, Y is in position 2, 4 or 6 of the nucleus, n is 0 or an integer in the range of 1 and 3 inclusive with the proviso that when n is 2 or 3 at least one Y is halogen, Z is halogen of atomic number 9 to 35 or alkyl of one to about four carbon atoms and a is 0, an integer in the range of 1 and 5 inclusive when Z is halogen, or 1 when Z is alkyl. These ureas are herbicidal. Ureas of the formula:

United States Patent [191 Brown NOV. 13, 1973 N-ARYL-N-ALKYL-N-ARYLTHIO UREAS AS HERBICIDES [60] Division of Ser. No. 41,603, is a continuation-in-part of Ser. No. 709,896, March 4, 1969, abandoned, and a continuation-in-part of Ser. No. 3,238, Jan. 15,

1970, abandoned, said Ser. No. 3,238, Continuation-impart of Ser. No. 709,896.

[52] US. CL... 71/98, 7l/76 [51] Int. Cl. A0ln [58] Field of Search 71/98; 260/453 R [56] References Cited UNITED STATES PATENTS 3,332,975 7/1967 Bauer et a1 260/453 R 3,165,549 1/1965 Martin et a1 71/120 3,497,541 2/1970 Martin et a1 71/120 3,276,855 10/1966 Richter 71/98 2,655,445 10/1953 Todd 71/120 3,309,192 3/1967 Luckenbaugh 71/120 FOREIGN PATENTS OR APPLICATIONS 965,512 7/1964 Great Britain 260/453 R Primary Examiner-Glennon H. l-lollrah Att0rney--G. F. Magdeburger et a1.

[57] ABSTRACT Ureas of the formula:

where R is alkyl of one to about four carbon atoms, Y is halogen of atomic number 9 to 35, i.e., F, C1 and Br, alkyl of one to four carbon atoms, alkoxy of one to four carbon atoms or trifluoromethyl, with the proviso that when Y is alkyl or alkoxy, Y is in position 2, 4 or 6 of the nucleus, n is 0 or an integer in the range of 1 and 3 inclusive with the proviso that when n is 2 or 3 at least one Y is halogen, Z is halogen of atomic num her 9 to 35 or alkyl of one to about four carbon atoms and a is 0, an integer in the range of 1 and 5 inclusive when Z is halogen, or 1 when Z is alkyl. These ureas are herbicidal.

18 Claims, No Drawings N-ARYL-N-ALKYL-N-ARYLTI-IIO UREAS AS HERBICIDES CROSS REFERENCE TO RELATED APPLICATIONS This application is a division of application Ser. No. 41,603, filed May 28, 1970, now US. Pat. No. 3,697,572, which is a continuation-in-part of copending application Ser. No. 709,896, filed Mar. 4, 1969 now abandoned, and a continuation-in-part of copending application Ser. No. 3,238, filed Jan. 15, 1970 now abandoned. Application Ser. No. 3,238 is a continuation-in-part of application Ser. No. 709,896.

FIELD OF INVENTION This invention concerns a novel group of aromatic ureas and their use as herbicides. More particularly it concerns N-aryl-N-alkyl-N'-arylthio ureas and their use as herbicides.

INVENTION DESCRIPTION The herbicidal ureas of this invention may be represented by the formula:

where R is alkyl of one to about four carbon atoms, Y is halogen of atomic number 9 to 35, i.e., F, Cl and Br, alkyl of one to about four carbon atoms, alkoxy of one to about four carbon atoms or trifluoromethyl, with the proviso that when Y is alkyl or alkoxy, it is in position 2, 4 or 6 of the nucleus, n is or an integer in the range of l and 3 inclusive with the proviso that when n is 2 or 3 at least one Y is halogen, Z is halogen of atomic number 9 to 35 or alkyl of one to about four carbon atoms and a is 0, an integer in the range of l and inclusive when Z is halogen, or 1 when Z is alkyl. The Ys and 2's wherein n and a are integers greater than 1 may be the same or different.

Because of their exceptional herbicidal activities the compounds wherein R is methyl, a is 1 Z is in position 4 of the benzene nucleus and is hydrogen, chlorine or alkyl of one to four carbon atoms and (a) when n is 1, Y is fluorine in position 2 or chlorine in position 4 or (b) when n is 2, one Y is chlorine in position 3 and the other Y is chlorine or bromine in position 4, are preferred. These preferred compounds may be represented by the formulas:

wherein Z is Cl, hydrogen or alkyl of one to four carbon atoms and Y is chlorine in position 4 or fluorine in position 2, and

wherein Z is as defined previously and Y is Cl or Br. The compounds of formulas 2 and 3 wherein Z is chlorine are particularly preferred.

Examples of ureas represented by formula (1) are: N-m-bromophenyl-N '-propyl-N '-p-bromophenylthio urea, N-o-fluorophenyl-N -butyl-N '-pchlorophenylthio urea, N-2,6-dichloro-4- methylphenyl-N'-methyl-N-p-bromopheny]thio urea, N-2-bromo-4-methoxyphenyl-N'-isopropyl-N-4- ethylphenylthio urea, N-2,4,6-trichlorophenyl-N'- butyl-N'-2,5-dichlorophenylthio urea, N-2-methyl-3,4- difluorophenyl-N'-methyl-N-p-fluorophenylthio urea N-p-ethylphenyl-N '-methyl-N '-3 ,4-dibromophenyltio urea, N-p-cumyl-N -n-butyl-N '-p-chlorophenylthio urea, N-p-butylphenyl-N '-methyl-N pentachlorophenylthio urea, N-o-ethoxyphenyl-N- methyl-N'-tolylthio urea, N-p-butoxyphenyl-N'-ethyl- N'-p-chlorophenylthio urea, N-2,4,6-tribromophenyl- N-propyl-N-p-cumylthio urea, N-p-ethylphenyl-N- butyl-N'-p-butylphenylthio urea, N-p-ethoxyphenyl- N-ethyl-N-2,4,6-trichlorophenylthio urea, N-2- chloro-4-butylphenyl-N-methyl-N'- pentabromophenylthio urea, N-4-butoxy-2,6- difluorophenyl-N '-methyl-N '-3 ,4-difluorophenylthio urea and N-p-methoxyphenyl-N-propyl-N'-2,4,6- trifluorophenylthio urea.

The above described ureas may be prepared by reacting a urea with a sulfenyl halide according to the following equation:

wherein X is' halogen, preferably chlorine, and Y, R, Z,

n and a are as previously defined. This reaction may be carried out in pyridine, dimethyl formamide with or without an acid acceptor or other solvents such as methylene chloride, chloroform, acetonitrile and dimethoxyethane using an acid acceptor. Acid acceptors which may be used with dimethyl formamide and these other solvents are pyridine, alkylpyridines, quinoline and similar heterocyclic bases. Pyridine-is a preferred acid acceptor. When pyridine is used alone it acts both as a solvent and acid acceptor. The preferred medium for carrying out this reaction is'dimethyl formamide with pyridine as an acid acceptor.

The pressures and temperatures at which the reaction is carried out are not critical. Since the reaction is slightly exothermic, temperatures ranging from ambient to about 60C. will normally be used. However, lower temperatures or higher temperatures up to the decomposition temperature of .the reactants and product may be used; For convenience the pressure will usually be atmospheric or autogenous. The reaction will normally be complete within 30 minutes to 4 hours.

The urea reactant in the'above equation may be prepared in situ or beforehand. Conventional methods such as reacting an amine with an isocyanate may be used to prepare this reactant.

EXAMPLES The following examples illustrate two methods which may be used to prepare the ureas of this invention. These examples are in no way intended to limit the invention described herein. Unless otherwise indicated, percentages are by weight.

EXAMPLE 1 trated HCl in one liter of ice water. The organic materil als in the mixture were extracted with 500 g. of methylene chloride. The extract was washed with dilute HCl, saturated Nal lCO solution and water, dried and stripped to an orange oil which crystallized slowly. This solid was recrystallized from a mixture of 50 ml. of ben- 15 zene and 100 ml. of hexane. The recrystallized product added to the mixture to form a solid precipitate. The mixture was filtered and the solid was washed with water and hexane and air dried. The dried solid weighed 39 g. Gas liquid chromographic analysis of this solid indicated it was essentially pure N-pchlorophenyl-N-methyl-N-p-chlorophenylthio urea. This compound melted at 85-96C. and its sulfur and chlorine analyses were:

Calculated: S: 9.80%; Cl: 21.80%

Found: S: 9.99%; Cl: 21.35% This compound was purified by recrystallization from benzene and hexane. The purified compound melted at 9598C.

Other ureas included within this invention were prepared using one or more of the methods described above. These compounds are listed in Table l.

TABLE I Element analyses S Cl Melting point Compound Cale. Found Calc. Found N-2,5-dichloropheny1-Nmethyl-N-phenylthi0urea 9. 78 9. 76 21. 65 21. 62 59-61 N -2,5-dichlorophenyl-N-methyl-N-p-chlor0pheny1thi0 urea 8. 86 9. 21 29. 45 28. 82 125-128 N-p-tolyl-N-rnethyl-N'-phenylthio urea 11.75 11. 68 10. 3 9. 98 65-68 N-p-tolyl-N"methyl-N-p-chl0rophenylthi0 urea 10. 4 10. 68 11.57 12.25 72-75 N -m-chlorophenyl-N-metl1yl-N-phenylthio urea 10.9 10. 95 12. 1 12. 28 64-67 N -p-methoxyphenyl-N-methyl-N-phenylthio urea 11. 10 11. 08 53-55. 5 N p-methoxyphenyl-N-methy1-N -p-ehl0r0pl1enylthio urea 9. 92 10. 18 11. 00 11. 42 85-87 N-3,4-dichlor0phonyl-N-methyl-N-phenylthio urea 9. 78 9. 92 21. 7 21. 72 102-195 N-3,4-dichlorophenyl-N-ethy1 N-phenylthi0 urea- 9. 39 9. 52 20. 8 20. 32 51. 5-55 N-p-ohlorophenyl-N-rnetl1yl-N-phenylthio urea 10.85 10.92 12. 1 11.72 74-78 N-3,4-dichlor0phenyl-N-ethyl-N-p-chlorophenylthi0 urea- 8. 51 8. 57 28. 2 27. 65 85-86. 5 N-m-chlorophenyl-N-methyl-N-p-tolythio urea 10. 4 10.13 11.6 12. 32 69-69 N-phenyl-N-methy1-N"p-chlorophenylthio urea... 10.9 10.77 12.1 12.30 65-70 N-p-chrophenyl-N-ethyl-N-p-ohlorophenylthio urea 9. 4 9. 8O 20. 8 21. 62 61-64 -phenyl-N-methy1-N-p-to1y1thio urea 11.73 11.52 10. 26 10.52 70-73 N-O-chloropllenyl-N'-methyl-N-p-chl0rophenylthi0 urea. 9. 80 10. 13 21. 65 21. 68 79-83 N-3,-diehlorophenyl-N-methyl N'-p-tolylthio urea 9. 38 9. 23 20. 8 20. 52 95-97 N -pchlorophenyl-N -methyl-N-p-tolylthio urea 10 4 10. 62 11. 55 101- 10 3 N -m-chlorop11enyl-N-methyl-N-p-chlorophenylthio urea. N-3,4-dichlorophenyl-Nmethyl-N-p-chlorophenylthio ure N-phenyl-N-methy1-N-phenylthi0 urea 2 3 N -p-bromopl1enyl-N-methyl-N -phenylthio urea 9. 5 N -p-bromophenyl-N' -motl1y1-Np-chlorophenylthio urea 8. 61 N-3,4-dichlorophenyl-N-rnothyl-N-pentaehlorophenylthio urea. 6. 11 N-3,5-dichlorophenyl-N'-methy1-N-pl1eny1thio urea 9. 79 N-methyl-N-phenylthio-N-o-flu0rophenyl urea 11. 59 N-n1-trifluoromethylphenyl-N-metl1yl-N'-p-ohlorophenylthio urea 8. 87 N-m-trifluoromethylphenyl-N-methyl-N-p-tolylthio urea 9. 42 N-o-l'luorophenyl-N'-methy1-N-p-tert.butylphenylthi0 urea. 9. 63 N-o-tolyl-N-methyl-N-p-ohlorophenylthio urea 10. 42 N-O-trifiuoromethylphenyl-N-methyl-Np-chl0r0phenylthi0 urea. 8. 87 N-3,5-dichl0rophenyl-N'-methyl-N-p-chl0r0phonyltl1i0 urea 8. 85 N-o-fluor0pheny1-N-methylN -p-chlorophenylthio urea 10. N-p Iluorophenyl-N -methyl-N -p-ohl0ropheny1thio urea. 10. 30 N-m-fluorophenyl-N -mot11yl-Nirchlorophonylthio urea 10. 30 N-2,4-di fiuorophenyl-N-methy1-N'-p-chlorophenylthio urea 9. 73 N-2-fluoro-5-trifiuoromethylphenyl-N-methyl-N-pchlorophenylthro urea. 8. N -3-ohloro-4-br0mophenyl-N-methyl-N-p-ohlorophenylthio urea. 7. 88 N-3-lluoro4-bromophenyl-N -methyl-N-p-chlorophenyltl1io urea 8.21 N o-I1u0rophenyl-N-met.hyl-N-p-tolylthio urea 11.02 N-2-1l110r0-4-brom0phenyl-N-methyl-N-p-chlorophenylthi0 urea 8. 21 N-2-lluoro4-chlorophenyl-N-methyl-N-p-ohlorophenylthio urea... 9. 28 NB-fiu0ro-4-chl0rophenyl-N-methyl-N pehlorophenylthio urea 9. 28

Nitrogen rather than chlorine. "Chlorine and bromine in meq./g.

was washed with ml. of hexane to give 21.6 g. of N- UTILITY p-chlorophenyl-N '-methyl-N '-p-chlorophenylthio urea. lts melting point was 94-97C.

EXAMPLE 2 chlorophenylsulfenyl chloride was added to this mix-' ture. The temperature of the mixture increased slightly during this addition, but it did not exceed 40C. The

combined mixture was then stirred at ambient temperature for 1 hour. After this time 1 liter of ice water was The ureas of this invention are, in general, herbicidal in both preand post-emergence applications. For preemergence control of undesirable vegetation these ureas will be applied in herbicidal quantities to the environment, e.g., soil infested with seeds and/or seedlings of such vegetation. Such application will inhibit the growth of or kill the seeds, germinating seeds and seedlings. They are applied directly to the foliage and other plant parts in post-emergence applications. Generally they are effective against weed grasses as well as broadleaved weeds. Some may be selective with respect to type of application and/or type of weed.

Preand post-emergence herbicidal tests on representative ureas of this invention were made using the following methods:

Pre-Emergence Test An acetone solution of the test urea was prepared by mixing 750 mg. urea, 220 mg. surfactant and 5 m1. acetone. This solution was added to ca. 125 ml. water containing 156 mg. surfactant.

Seeds of the test vegetation were planted in a pot of soil and the urea solution was sprayed uniformly onto the soil surface at a dose of 200 micrograms per cm*. The pot was watered and placed in a greenhouse. The pot was watered intermittently and observed for seedling emergence, health of emerging seedlings, etc., for a 3-week period. At the end of this period the herbicidal effectiveness of the urea was rated based on the physiological observations. A 0 to 100 scale was used; 0 representing no phytotoxicity, 100 representing com- This formulation was uniformly sprayed on 2 replicate pots of 24-day-old test plants (c.a. -25 plants per pot) at a dose of I00 micrograms/cm. After the plants had dried, they were placed in a greenhouse. The plants were watered intermittently at their .bases as needed and observedperiodically for phytotoxic effects and physiological and morphological responses to the treatment. After 3 weeks, the herbicidal effectiveness of the urea was rated based on these observations. A 0 to 100 scale was used; 0 representing no phytotoxicity, 100 representing complete kill.

The results of these tests appear in Table II. For comparison the structurally related compounds, N-pchlorophenylthio-N-p-chlorophenyl urea, N,N- dimethyl-N-p-chlorophenylthio urea and N-methyl-N- p-chlorophenylthio urea, were also tested by the above described methods. These test results also appear in Table II.

TABLE II Com pound N-2,5- llchlorophcnyl-N-mnthyl-N-phenylthio urea N-3,4-dichlorophenyl-N-methyl-N-tolylthio urea N-p-chlorophenyl-N'-methyl-N-p-tolylthi0 urea N-m-chlorophenyl-N'-p-chl0r0phenylthi0-I I'-metl1yl urea. N-3,4-dicl1lorophenyl-N-p-chlorophenylthi0-N-methylure N-phenyl-N-methylN'-phenylthio urea N-3,4-dichlorophenyl-N'-methyl-N-pentachlorophenylth1o urea- N-p-bromopheny1-N-methy1-N-phenylthio urea N-p-bromophenyl-N-methyl-N-p-chlorophenyltliio urea. N-3,5-dichlorophenyl-N-methyl-N-phenylth10 urea N-methyl-N-phenylthio-No-fluorophenyl urea N-m-trilluoromethylphenyl-N-methyl-N-p-chlorophenylth1o urea N-m-trl fluoromethylphenyl-N -methy1-N -p-toly1thi0 urea N-o-fluorophenyl-N-rnethyl-N-p-tert.butylphenylthio urea N-o-tolyl-N-methyl-N-p-chlorophenylthio urea N-3-chloro-4-bromophenyl- N-3-fluoro-4-bromophenyl-N'-methyl-N pahlorophenylthro urea N-2-iluoro-4-bromophenyl-N-methyl-N-p-chlorophenylthio urea...

N-2-fluoro-4-chlorophenyl-N'-methyl-N'-p-chlorophenylthio urea 100/100 COMPARISON TESTS Herbicidal effectiveness pre/post O R C W M P L Concentration was 100 micrograms/cm. in pre-emergence test. Active in pro-emergence application only on broadleaf weeds. Eflective only in pust-emergence application.

Nora-O =Wi1d oats (Avena fatua); R=Annual ryegrass (Lolium multiflomm); C=Crabgrass (Digitaria sanguinalis) W=Watergrass (Echinochlo:

trwafl M=Mustgrd fflqssice erqensis); P=Pigweed (Amaranthus retroflezus); L=Lambsquarter (ql enopodium album I plete kill.

Post-Emergence Test The test urea was formulated in the same manner as described above for the Pre-Emergence Test. The concentration of urea in this formulation was 5,000 ppm.

As illustrated by the above data the preferred com- TABLE III Post-Emergence activity Preferred Compounds v. Analogs Conc., Compound meg/cm. R W* L" I M Preferred compounds:

N-p-ehlorophenyl-N-methyl-N-p-chlorophenylthio urea 11 100 100 92 100 100 100 3. 7 53 13 58 100 100 100 N-p-chlorophcnyl-N'-methyl-N-p-tolylthi0 urea 11 100 100 100 100 100 100 N -3,4-1iehlorophenyl-N -methyl-N -phenylthi0 urea. 11 76. 7 100 100 100 100 100 3. 7 38. 3 71. 7 85 100 100 100 N-3,4-dichlorophenyl-N-methyl-N-p-tolylthio urea 11 100 92 100 100 100 100 3. 7 70 35 50 100, 100 100 N-ZSA-diehlorophenyl-N-methyl-N-p-ehlorophenylthio urea 11 62 100 100 100 100 100 3. 7 3 72 65 100 100 100 N-o-fluorophenyl-N-n1ethyl-N-p-ch1orophenylthio urea 11 100 100 100 100 100 nalogs: I

N-phenyl'N-methyl-N-p-tolylthio urea 11 95 97 92 100 100 100 3. 7 17 17 33 100 100 100 N-phenyl-N-methyl-N-p-oh1orophenylthio urea 11 100 97 95 100 100 100 3. 7 27 32 37 100 87 100 N-m-chloropheny1N-metl1yl-N-p'ehlorophenylthio urea 11 87 100 0 97 100 3. 7 0 0 0 0 0 '37 N-3,6-dichlorophenyl-N-methy1-N-p-ch1orophenylthio urea 11 0 0 75 100 v 3. 7 o 0 43 18 0 N-p-fluorophenyl-N -methyl-N-p-chloropl1eny1thio urea 11 33 90 60 98 3. 7 40 10 75 55 73 N-m-fluorophenyl-N-methyl-N-pchloropheny1thio urea 11 70 100 100 100 3. 7 25 25 100 40 1 00 "See note at end of Table II. I m

One of the preferred compounds, N-3-bromo-4- chlorophenyl-N'-methyl-N'-p-chlorophenylthio urea, showed remarkable selectivity between broadleaves and grasses in post-emergence application. For instance, at a dosage level of 3.7 micrograms/cm this compound was completely inactive against grasses but provided 97 percent, 100 percent and 97 percent control of lambsquarter, pigweed and mustard, respectively. On this basis, the N-3-bromo-4-chl0rophenyl compounds are included in the preferred subgenus of formula 3 above.

The preferred compounds of formula 1 above in which Y is fluorine in position 2 are also generally better than their analogs in pre-emergence applications. This superiority is illustrated by the data in Table IV below.

TABLE IV Pre-Emergence Activity Conc., Compound mcg./em. 0* W" L I" M* Preferred compounds:

N-o-fiuorophenyl-N -methyl-N-p-chl0ropheny1thio urea 11 100 100 07 100 100 3. 7 95 100 98 100 100 I I I 1. 2 100 05 N -methyl-N-pheny1thi0-N-o-fluorophenyl urea 11 100 100 93 100 99 3. 7 100 97 87 100 99 Analogs:

N-phenyl-N-p-chlorophenylthio-N-methyl urea 11 97 85 87 100 100 3. 7 57 40 100 100 1. 2 95 50 N-m-fluorophenyl-N-methyl-N'-p-chloropheny1thio urea 11 100 90 80 100 100 3. 7 50 33 40 77 88 I 1'. 2

N-p-fluorophenyl-N-methyl-N-p-chlorophenylthio urea 11 97 98 97 100 100 3. 7 40 93 83 97 93 N-o-chlorophenyl-Nmetl1yl-N-p-chlorophenylthi0 urea 11 7 7 37 45 3. 7 0 0 7 0 8 N-phenyl-N-methyl-N-pheny1th1o urea 11 100 98 92 100 100 3. 7 68 100 *Seonoto at end of Table II.

The data in Table IV show that said compounds of formula 2 are better pre-emergence herbicides than their analogs in which the N-phenyl group is unsubstituted, the position of the fluorine atom is-changed or the fluorine atom is replaced with a chlorine atom.

The amount of urea administered will vary with the particular plant part or plant growth medium which is to be contacted, the general location of application, i.e., sheltered areas such as greenhouses as compared to exposed areas such as fields, as well as the desired type of control. For pre-emergent control of most plants dosages in the range of about 0.5 to 20 lbs. per acre will be used. Such administration will give a concentration of about 2 to 80 ppm. urea distributed throughout 0.] acre-foot. For post-emergence application, such as foliar spray application, compositions containing about 0.5 to 8 lbs. urea per 100 gal. spray will be used. Such application is equivalent to about 0.5 to 20 lbs. urea per acre.

The herbicidal compositions of this invention comprise a herbicidal amount of one or more of the above described ureas intimately admixed with a biologically inert carrier. The carrier may be a liquid diluent such as water or acetone or a solid. The solid may be in the form of dust, powder or granules. These compositions will also usually contain adjuvants such as a wetting or dispersing agent to facilitate their penetration into the plant growth media or plant tissue and generally enhance their effectiveness. These compositions may also contain other pesticides, stabilizers, conditioners, fillers and the like.

As will be evident to those skilled in the art, various modifications on this invention can be made or followed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the following claims.

l claim:

l. A method for controlling the growth of undesirable vegetation which comprises applying to the locus thereof a herbicidally effective amount of the urea of the formula: 7

where R is alkyl of one to about four carbon atoms, Y is halogen of atomic number 9 to 35, i.e., F, Cl and Br, alkyl of one to four carbon atoms, alkoxy of one to four carbon atoms of trifluoromethyl, with the proviso that when Y is alkyl or alkoxy, said alkyl or alkoxy is in position 2, 4 or 6 of the nucleus, n is or an integer in the range of l and 3 inclusive with the proviso that when n is 2 or 3 at least one Y is halogen, Z is halogen of atomic number 9 to 35 or alkyl of one to four carbon atoms and a is 0, an integer in the range of l and inclusive when Z is halogen, or 1 when Z is alkyl.

2 The method of claim 1 wherein R is methyl, a is 1, Z is in position 4 of the benzene nucleus and is hydrogen, chlorine or alkyl of one to four carbon atoms and (a) n is l and Y is fluorine in position 2 or chlorine in position 4 or (b) n is 2 and one Y is chlorine in position 3 and the other Y is chlorine or bromine in position 4.

3. The method of claim 2 wherein Z is in position 4 and is chlorine.

4. The method of claim 1 wherein R is methyl, a is 1, Z is chlorine in position 4, n is 1 and Y is fluorine in position 2.

5. The method of claim 1 wherein R is methyl, a is 1, Z is in position 4 and is chlorine, n is 2 and one Y is chlorine in position 3 and the other Y is chlorine in position 4.

6. The method of claim 1 wherein R is methyl, a is 1, Z is tert. butyl in position 4, n is 1 and Y is fluorine in position 2.

7. The method of claim 1 wherein R is methyl, a is 0, n is 2 and one Y is chlorine in position 4 and the other Y is chlorine in position 3.

8. The method of claim 1 wherein R is methyl, a is 0, n is 1 and Y is fluorine in position 2.

9. The method of claim 1 wherein R is methyl, a is 1, Z is chlorine in position 4, n is 2 and one Y is chlorine in position 3 and the other Y is bromine in position 4.

l0. Herbicidal composition comprising an effective amount of the urea of the formula:

where R is alkyl of one to about four carbon atoms, Y is halogen of atomic number 9 to 35, i.e. F, Cl and Br, alkyl of one to four carbon atoms, alkoxy of one to four carbon atoms or trifluoromethyl, with the proviso that when Y is alkyl or alkoxy, said alkyl or alkoxy is in position 2, 4 or 6 of the nucleus, n is 0 or an integer in the range of 1 and 3 inclusive with the proviso that when n is 2 or 3 at least one Y is halogen, Z is halogen of atomic number 9 to 35 or alkyl of one to four carbon atoms and a is 0, an integer in the range of l and 5 in- ,clusive when Z is halogen, or 1 when Z is alkyl, ad-

mixed with a biologically inert carrier therefor.

11. Composition of claim 10 wherein R is methyl, a is 1, Z is in position 4 of the benzene nucleus and is hydrogen, chlorine or alkyl of one to four carbon atoms and (a) n is l and Y is fluorifne in position 2 or chlorine in position 4 or (b)-n is 2 and one Y is chlorine in position 3 and the other Y is-chlorine or bromine in position 4.

12. Composition of claim 11 wherein Z is in position 4 and is chlorine.

l3. Composition of claim 10 wherein R is methyl, a is 1, Z is chlorine in position 4, n is 1 and Y is fluorine in position 2.

l4. Composition of claim 10 wherein R is methyl, a is 1, Z is in position 4 and is chlorine, n is 2 and one Y is chlorine in position 3 and the other Y is chlorine in position 4.

l5. Composition of claim 10 wherein R is methyl, a is 1, Z is tert. butyl in position 4, n is l and Y is fluorine in position 2.

l6. Composition of claim 10 wherein R is methyl, a is 0, n is 2 and one Y is chlorine in position 4 and the other Y is chlorine in position 3.

l7. Composition of claim 10 wherein R is methyl, a is 0, n is l and Y is fluorine in position 2.

l8. Composition of claim 10 wherein R is methyl, a is 1, Z is chlorine in position 4, n is 2 and one Y is chlorine in position 3 and the other Y is bromine in position 4. 

2. The method of claim 1 wherein R is methyl, a is 1, Z is in position 4 of the benzene nucleus and is hydrogen, chlorine or alkyl of one to four carbon atoms and (a) n is 1 and Y is fluorine in position 2 or chlorine in position 4 or (b) n is 2 and one Y is chlorine in position 3 and the other Y is chlorine or bromine in position
 4. 3. The method of claim 2 wherein Z is in position 4 and is chlorine.
 4. The method of claim 1 wherein R is methyl, a is 1, Z is chlorine in position 4, n is 1 and Y is fluorine in position
 2. 5. The method of claim 1 wherein R is methyl, a is 1, Z is in position 4 and is chlorine, n is 2 and one Y is chlorine in position 3 and the other Y is chlorine in position
 4. 6. The method of claim 1 wherein R is methyl, a is 1, Z is tert. butyl in position 4, n is 1 and Y is fluorine in position
 2. 7. The method of claim 1 wherein R is methyl, a is 0, n is 2 and one Y is chlorine in position 4 and the other Y is chlorine in position
 3. 8. The method of claim 1 wherein R is methyl, a is 0, n is 1 and Y is fluorine in position
 2. 9. The method of claim 1 wherein R is methyl, a is 1, Z is chlorine in position 4, n is 2 and one Y is chlorine in position 3 and the other Y is bromine in position
 4. 10. Herbicidal composition comprising an effective amount of the urea of the formula:
 11. Composition of claim 10 wherein R is methyl, a is 1, Z is in position 4 of the benzene nucleus and is hydrogen, chlorine or alkyl of one to four carbon atoms and (a) n is 1 and Y is fluorine in position 2 or chlorine in position 4 or (b) n is 2 and one Y is chlorine in position 3 and the other Y is chlorine or bromine in position
 4. 12. Composition of claim 11 wherein Z is in position 4 and is chlorine.
 13. Composition of claim 10 wherein R is methyl, a is 1, Z is chlorine in position 4, N is 1 and Y is fluorine in position
 2. 14. Composition of claim 10 wherein R is methyl, a is 1, Z is in position 4 and is chlorine, n is 2 and one Y is chlorine in position 3 and the other Y is chlorine in position
 4. 15. Composition of claim 10 wherein R is methyl, a is 1, Z is tert. butyl in position 4, n is 1 and Y is fluorine in position
 2. 16. Composition of claim 10 wherein R is methyl, a is 0, n is 2 and one Y is chlorine in position 4 and the other Y is chlorine in position
 3. 17. Composition of claim 10 wherein R is methyl, a is 0, n is 1 and Y is fluorine in position
 2. 18. Composition of claim 10 wherein R is methyl, a is 1, Z is chlorine in position 4, n is 2 and one Y is chlorine in position 3 and the other Y is bromine in position
 4. 